Software defined networking (SDN for short) is going to be an important technology that will change the way we do networking. But what is SDN today and even more important, what is it going to be?

When you start reading about SDN as a network engineer, you ask yourself what your future job will look like. Will you still be a network engineer as we know you today, or a network developer, with a focus on scripting and programming your network? In my opinion, the reality will be somewhere in between. But no one can tell you today what impact SDN will have on your daily work tomorrow.

To give us a clearer perspective, let's compare SDN to a trend that began in 2010. Five years ago everyone started talking about "the cloud". Nobody knew what the cloud was, what it meant or what we should do with it. But everyone was talking about it. Every IT related event, blog or magazine was spending effort in writing about the cloud, and many engineers grew frustrated about the hype. Today, everyone is using the cloud and everyone knows what it is. Compare "the cloud" hype five years ago to the SDN hype today. SDN is new and there is a lot of talk and speculation. Over time we will gain understanding. SDN today is what cloud 5 years ago was.

But still, what will SDN be? Let's look back one more time, to 20 years ago. Cisco was a network equipment vendor, developing routers, switches and firewalls. Although the equipment has evolved over time -routers and switches can process more data, have more bandwidth and fancy new protocols -the way we do networking today is still the same as 20 years ago. We still configure a network on a per-device basis. When we roll out new applications or servers, we still have to configure every related network device, one by one. This can takes weeks, months, sometimes ages, just to configure the network.

Every other part in the IT infrastructure has developed. Spinning up a server takes just minutes, where before it took days. Delivering storage to your servers takes minutes or hours, instead of days or weeks. But the way we do networking is still the same.

Now we have to see the network as one single identity where applying changes is easy, straight forward and fast. We don't want any more single device configuration. We don't want to wait weeks or months for the network to be ready. It has to be done in minutes or hours.

SDN is a solution for our most important problems: duration of applying changes and complexity. But it will not be a solution for all our problems. We're still working with people and processes. Even with SDN, we still have to comply with all ITIL processes. If your change rate is very low, there will be no need for SDN. If you have a high change rate but your network consists of only a few devices, there is no need for SDN. Larger networks with high change rates are currently the best use cases for implementing SDN.

To conclude, the way we do networking nowadays has not evolved in the last 20 years. We are still doing CLI configurations on each single device and the network is far from being a single identity. SDN is a methodology to fix the way we do networking, and get us back to the future.